/Engine/Plugins/Developer/Concert/ConcertMain/Source/Concert/Public/IConcertServerEventSink.h
Destroyed in this case means that the resources for the session should be closed/freed, but not that persistent data should be deleted from disk.
void OnArchivedSessionDestroyed ( const [IConcertServer](API\Plugins\ConcertServer\IConcertServer) & InServer, const [FGuid](API\Runtime\Core\Misc\FGuid) & InArchivedSessionId )